The invention relates to the catalytic polymerization of ethylene with particularly produced high activity Mg and Ti containing complex catalysts in a low pressure gas phase process to produce polymers having a density of .gtoreq.0.91 to .ltoreq.0.97, a melt flow ratio of .gtoreq.22 to .ltoreq.32, a bulk density of 18 to 32 lbs/ft.sup.3 and controlled particle shape and size.